Help with a calculator script

bc2013 · March 15, 2010

I am writing a calculator script for a friend of mine but keep getting an error. I need to pass some values to the handle.php script and then do more calculations in that script. I am new to php and never written a script like this. Thank you for your time. I will paste the scripts below and the error.

The HTML page:

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<head>

<title>Untitled Document</title>

</head>

<body>

<u>Owner Operator Calculator</u><br />

Total Miles: <input type="text" name="miles" size="5" />

<br>

Payment: <input type="text" name="payment" size="5" />

<br>

Truck's MPG: <input type="text" name="milesPerGallon" size="5" />

<br>

Fuel Price: <input type="text" name="gasPrice" size="5" />

<br>

</form>

</center>

</body>

</html>

The handle.php page:

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<head>

<title>Untitled Document</title>

</head>

<body>

<?php // handle_oocalc.php

// address error handling

ini_set ('display_errors', 1);

error_reporting (E_ALL & ~E_NOTICE);

// IN CASE REGISTER_GLOBALS IS DISABLED

$payment = $_POST['payment'] ;

$milesPerGallon = $_POST['milesPerGallon'] ;

$gasPrice = $_POST['gasPrice'] ;

$miles = $_POST['miles'] ;

$gallonsNeeded = $_POST['gallonsNeeded'] ;

$totalFuelCost = $_POST['totalFuelCost'] ;

$netProfit = $_POST['netProfit'] ;

$dollarPerMile = $_POST['dollarPerMile'] ;

// Calculate the gallons needed for the trip

$gallonsNeeded = $miles / milesPerGallon;

// Calculate the total fuel cost

$totalFuelCost = $gallonsNeeded * $gasPrice;

// Calculate net profit

$netProfit = $payment - $totalFuelCost;

// Calculate dollar per mile

$dollarPerMile = $payment / $miles;

// Apply the proper formatting

$gallonsNeeded = number_format ($gallonsNeeded, 2);

$totalFuelCost = number_format ($totalFuelCost, 2);

$netProfit = number_format ($netProfit, 2);

$dollarPerMile = number_format ($dollarPerMile, 2);

// Print out the results

print " Here are the results:<br />

$gallonsNeeded gallons needed for the trip.<br/>

$totalFuelCost is the total fuel cost. <br/>

$netProfit is your net profit.<br/>

$dollarPerMile is the dollar per mile.<br/>";

?>

</body>

</html>

Here's the error I get:

Warning: Division by zero in /home/lvfoo0/public_html/handle_oocalc.php on line 33

Here are the results:

0.00 gallons needed for the trip.

0.00 is the total fuel cost.

1,000.00 is your net profit.

0.83 is the dollar per mile.

Again, thank you for your time.

darkfreaks · March 15, 2010

first off

$gallonsNeeded = $miles / milesPerGallon;

needs to be:

$gallonsNeeded = $miles / $milesPerGallon;

also try checking if empty or anything that would make it equal zero

if(empty($miles) && empty($milesPerGallon))
{
print("sorry but you do not have enough miles or miles per gallon");
}

darkfreaks · March 15, 2010

on another note if that doesnt work you can supress that error by doing

$gallonsNeeded = @$miles / $milesPerGallon;

bc2013 · March 15, 2010

Thanks alot dark. I thought I wasnt even close and its just one little thing. Now where do I put that empty code? And can I put all of the form variables in that one statement and use the || instead of the &&? Thanks again

darkfreaks · March 15, 2010

of course you can use or || instead of and && or checks either one while and && checks both of them at once.

you can put it anywhere after you have defined both variables i suppose.

if($miles==''||empty($miles)) {
// echo error message here.
}

if($milesPerGallon==''||empty($milesPerGallon))
{
//echo error message here
}

bc2013 · March 16, 2010

Ok I got that and this is how I coded it:

if($miles==''||empty($miles))

{

print("You left the miles field blank.");

}

if($milesPerGallon==''||empty($milesPerGallon))

{

print("You left the MPG field blank.");

}

if($payment==''||empty($payment))

{

print("You left the payment field blank.");

}

if($gasPrice==''||empty($gasPrice))

{

print("You left the fuel price field blank.");

}

Now how can I code it so it will basically kill the script? Because now it is printing the error message that I told it to output but it is still doing the calcultions. I guess what I'm asking is how do I just get it to print that message and put a "back" link to the previous page? Thanks again

darkfreaks · March 16, 2010

why don't you put the form inside a PHP variable then echo out the error and the form that way it echos out on the same page

example:

$form="
<form action="handle_oocalc.php" method="post">

Total Miles: <input type="text" name="miles" size="5" />
<br>
Payment: <input type="text" name="payment" size="5" />
<br>
Truck's MPG: <input type="text" name="milesPerGallon" size="5" />
<br>
Fuel Price: <input type="text" name="gasPrice" size="5" />
<br>

<input type="submit" name="Submit" value="Calculate" onClick="return vldFrm_Feedback();" />

<input type="reset" value="Reset" />

</form>";

if($miles==''||empty($miles))
   {
   print("You left the miles field blank.$form");
   }

if($milesPerGallon==''||empty($milesPerGallon))
   {
   print("You left the MPG field blank.$form");
   }

if($payment==''||empty($payment))
   {
   print("You left the payment field blank.$form");
   }

if($gasPrice==''||empty($gasPrice))
   {
   print("You left the fuel price field blank.$form");
   }

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